The .NET team has fixed the issue and re-released the January 2018 Monthly Rollup for affected Windows versions as KB 4074880. Affected machines can be fixed by using one of the solutions described later in the document.

This document describes the symptoms and solutions to resolve the issue.

Re-launch your .NET Framework application(s) and note that the issue has been resolved.

Important Notes:

The Fixit tool is only meant to be used on affected systems. It will only complete the repair work on systems that match the applicability and symptoms described above.

If you are running the tool programmatically and/or want to check for success status via tool return codes, launch the tool as a new process and wait for it to terminate (e.g. “start /wait FixItTool-KB4074906.exe”). Depending on your systems management environment this may happen by default.

You can use the following commands to run the tool and determine the return code.

Solution 2 – Uninstall and re-install the January 2018 Monthly Rollup

The January 2018 Monthly Rollup has been re-released with a fix for this known issue. You will have a working system if you uninstall the initial Monthly Rollup (KB 4055002) and instead install updated January 2018 Monthly Rollup (KB 4074880).

Follow these steps:

In Control Panel, open the Windows Update item, and then select View update history.

Solution 3 – Replace GlobalUserInterface.CompositeFont Manually

Launch cmd as Administrator and navigate to %windir%\Microsoft.NET\Framework\v4.0.30319\WPF\Fonts and run:xcopy /y %USERPROFILE%\Downloads\GlobalUserInterface.CompositeFont .
(or copy and paste the GlobalUserInterface.Composite file through Windows Explorer to %windir%\Microsoft.NET\Framework\v4.0.30319\WPF\Fonts)

Launch cmd as Administrator and navigate to %windir%\Microsoft.NET\Framework64\v4.0.30319\WPF\Fonts and run:xcopy /y %USERPROFILE%\Downloads\GlobalUserInterface.CompositeFont .
(or copy and paste the GlobalUserInterface.Composite file through Windows Explorer to %windir%\Microsoft.NET\Framework64\v4.0.30319\WPF\Fonts).

Re-launch WPF application.

Reboot machine and re-launch application if you still have trouble.

Root Cause

The root cause of this problem is a MSI setup interaction between the .NET Framework January 2018 Rollup (KB4055002) and an already installed version of .NET Framework 4.7.1 product. The Rollup installer unexpectedly overwrites the 4.7.1 version of the GlobalUserInterface.CompositeFont file. This causes WPF operations that need this font file to fail.

All updates are extensively tested before they are provided to you. We are investigating the gap in our testing and will resolve that for our next release.